THE EIGHTEENTH CENTURy

Another Swede, Cronstedt (read in the Italian translation of 1779), reported a Latin list with division (see Wiedman) into alba sive pura (white that is pure) and mica colorata martialis (colored martial), which were further divided into varieties, including vitrum muscoviticum and talcum officinale. In a general description of the genus tnicaceous soils, in addition to the usual desc riptions of lamellae that are flexible and divisible into meshes, the behavior in fire was examined and said to cause loss of elasticity. It is also said that fusion with borax and alkaline salts creates a transparent glass, which is more easily obtainable with the martial types. 

An English translation of Cronstedfs book (1788) contained the same list of species and varieties cited previously, but also reported the chemical analysis of Kirwan as well as an observation by Fabroni, deputy-director of the Museum of Physics and Natural History of Florence. Fabroni observed that colored mica was dissolved by acqua regia or muriatic acid to produce a liquid that is yellow on account of iron. 

Around the some time the large treatise by Buffon (1790) appeared posthumously. His Histoire Naturelle des Mineraux in six vol umes is a work of vast size and of much higher quality than preceding ones. It not only provides a classification with relative descriptions of the species but it also considers genetic problems, alternating acute observations with inexplicable contradictions, such as interchanging mica and talc. There 

Thus ended the 1700s, the Age of Enlighten ment. Actually, there were times for enlightenment also for mineralogy, in general, and the micas in particular. The future 

The first three quarters of the 18 century were in the pre-scientific era of mineralogy, while the last quarter saw the beginning of scientific sophistication leading to our present knowledge. Not surprisingly, the simple descriptions of the external appearance of minerals (as imposed by the school of Werner) coexisted with references to their chemical nature. 

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Cholesterol was isolated m the eighteenth century but its structure is so complex that Its correct constitution was not determined until 1932 and its stereochemistry not verified until 1955 Steroids are characterized by the tetracyclic ring system shown m Figure 26 9a As shown m Figure 26 9b cholesterol contains this tetracyclic skeleton modified to include an alcohol function at C 3 a double bond at C 5 methyl groups at C 10 and C 13 and a C Hn side chain at C 17 Isoprene units may be discerned m var lous portions of the cholesterol molecule but the overall correspondence with the iso prene rule is far from perfect Indeed cholesterol has only 27 carbon atoms three too few for It to be classed as a tnterpene... 

Detailed information on the history of spices is available (4—6). Until the eighteenth century, the country or area that controlled the spice traffic was economically and politically the most powerful nation of the era. 

Systematic studies of membrane phenomena can be traced to the eighteenth century philosopher scientists. For example, Abbn Nolet coined the word osmosis to describe permeation of water through a diaphragm in 1748. Through the nineteenth and early twentieth centuries, membranes had no industrial or commercial uses but were used as laboratory tools to develop physical/chemical theories. 

It was not until the eighteenth century that carbon was recognized as a chemical element, and it is quite certain that no early metallurgist was aware of the basis of the unique properties of steel as compared to those of wrought iron. Carbon can be alloyed with iron in a number of ways to make steel, and all methods described herein have been used at various times in many locaUties for perhaps 3000 or more years. 

Until a few hundred years ago, sugar was strictiy a luxury item. Queen Elizabeth I is credited with putting it on the table in the now familiar sugarbowl, but it was so expensive that it was used only on the tables of royalty. Sugar production reached large volume at a reasonable price only by the eighteenth century. 

The first chromium compound was discovered in the Ural mountains of Russia, during the latter half of the eighteenth century. Crocoite [14654-05-8] a natural lead chromate, found immediate and popular use as a pigment because of its beautihil, permanent orange-red color. However, this mineral was very rare, and just before the end of the same century, chromite was identified as a chrome bearing mineral and became the primary source of chromium [7440 7-3] and its compounds (1) (see Chromiumand chromium alloys). 

Wolf, A., "A History of Science, Technology and Philosophy in the Eighteenth Century."... 

The hazards of chemicals are commonly detected in the workplace first, because exposure levels there are higher than in the general environment. In addition, the exposed population is well known, which allows early detection of the association between deleterious health effects and the exposure. The toxic effects of some chemicals, such as mercury compounds and soot, have been known already for centuries. Already at the end of the eighteenth century, small boys who were employed to climb up the inside of chimneys to clean them suffered from a cancer of the scrotum due to exposure to soot. This was the first occupational cancer ever identified. In the viscose industry, exposure to carbon disulfide was already known to cause psychoses among exposed workers during the nineteenth century. As late as the 1970s, vinyl chloride was found to induce angiosarcoma of the liver, a tumor that was practically unknown in ocher instances. ... 

Ethylene was known to chemists in the eighteenth century and isolated in pure form in 1795. An early name for ethylene was gaz olefiant (French for "oil-forming gas"), to describe the fact that an oily liquid product is formed when two gases—ethylene and chlorine—react with each other. 

General similarities and trends in the chemical properties of the elements had been noticed increasingly since the end of the eighteenth century and predated the observation of periodic variations in physical properties which were not noted until about 1868. However, it is more convenient to invert this order and to look at trends in atomic and physical properties first. 

Carbon known as a substance in prehistory (charcoal, soot) but not recognized as an element until the second half of the eighteenth century. 

The classic salt-cake method was introduced with the Leblanc process towards the end of the eighteenth century and is still used to produce HCl where rock-salt mineral is cheaply available (as in the UK Cheshire deposits). The process is endothermic and takes place in two stages ... 

The blast furnace (Fig. A, opposite) remains the basis of ironmaking though the scale, if not the principle, has changed considerably since the eighteenth century the largest modem blast furnaces have hearths 14 m in diameter and produce up to 10000 tonnes of iron daily. 

Origins of the science associated with thermal insulations coincide with the development of thermodynamics and the physics associated with heat transfer. These technical subjects date to the eighteenth century. Early obseiwations that a particular material was useful as thermal insulation were not likely guided by formal theoi y but rather by trial and error. Sawdust was used, for example, in the nineteenth centui y to insulate ice storage buildings. 

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